1. Field of the Invention
This invention relates to automatic washing machines for cleaning vertical surfaces, and in particular to an automatic window washer which is suspended from the top of a building by a suspension line to move up and down over the face of the building while cleaning the building windows.
2. Description of the Prior Art
In the past, the exterior of taller buildings were generally constructed from either stone or brick and were designed more ornately than more modern buildings. Often decorative portions of the building extended outwardly a considerable distance from the window surface. Furthermore, many of the taller old buildings were constructed with a step back so that the floor area of the building decreased as the building extended upwardly. The windows in these buildings were of the double-hung type which could be opened to provide ventillation within the building. These windows were generally manually cleaned by workmen, either standing on a staging, or sitting in a sling suspended from a suspension line anchored at the top of the building.
Buildings being constructed today are taller and less ornate than buildings constructed in the past. They are generally framed with structural steel and have a rather smooth or flat outer surface constructed from concrete, stone or metal panels. Moreover, the windows do not open, but are fixed, and constitute a larger percentage of the surface area of the building than was common in older buildings. Usually, the windows are arranged in vertical columns which are defined by vertical mullions interspaced between the windows. The windows, furthermore, are usually not inset very deeply in respect to the exterior surface of the adjacent non-glazed portions of the building exterior. Because of the relative increase in the window area of a building, the increased average height of buildings, and the increased wage rate for manual labor; the cost of manually cleaning the glazed area of a building has risen dramatically during the past decade. Also, due to the sheer height of many modern buildings and the substantial distance that they sway back and forth, the manual cleaning of windows has become more dangerous, thus enlarging the need for efficient automatic window washers.
Automatic window washers per se are not new. In general, these devices have consisted of means for spraying cleaning liquid onto windows being cleaned, a moving brush or roller for scrubbing the wetted windows, and means for removing the cleaning fluid and dirt from the windows. The means for removing the cleaning liquid from the windows have usually consisted of a squeegee or sponge to wipe the window. Also, a rapidly flowing air current generated by a blower or a vacuum source has been used by itself or in combination with a squeegee or sponge to blow or suck the cleaning liquid from the windows.
In operation these window washers have been moved up and down the face of a building by suspension cables. Following each vertical pass, an apparatus on the roof of the building to which the upper end of the suspension cable is attached is stepped into position sideways so that the next vertical pass of the window washer will be alongside the former vertical pass. The window washer itself may include a cable drum and a motor for raising and lowering the apparatus, or a cable drum and motor may be incorporated in the support apparatus located on the roof of the building. Furthermore, the window washer may include means for urging the scrubber brush, as a unit, into contact with the window being washed.
One disadvantage of at least some known automatic window washers is that they can satisfactorily clean a window only while moving in one direction, either only upwardly or only downwardly. This results in much time being wasted waiting for the apparatus to be retracted to its starting position. A second disadvantage of known automatic window washers is that they require a relatively large amount of water to clean a given window area. Because these devices generally spray the cleaning liquid directly on the window and because the scrubber brushes and removal means are generally not positioned very close to the location at which the cleaning liquid is sprayed on the window, a large amount of water is needed to adequately and uniformly wet the window and to keep the dirt particles in suspension in the cleaning liquid for a sufficient length of time to enable the removal means to collect the cleaning liquid and the suspended dirt prior to the cleaning liquid evaporating away. Furthermore, due to the limited amount of weight supportable by a suspension line support system, either (1) the window washer must be refilled quite often, perhaps even before making one pass, (2 ) the dirty used water must be recycled, or (3) a complicated filtration system must be used to clean the used water. Another disadvantage is that even if the window washer has means for advancing the scrubber forward into contact with the window, the scrubber unit as a whole can only be advanced or retracted in a direction normal to the face of the building. Thus, these window washers cannot satisfactorily clean windows which lie in a plane vertically askewed from the general plane of the building surface.
Examples of known automatic window washers are disclosed by the following U.S. patents: U.S. Pat. No. 1,416,280, granted May 16, 1922, to Joseph Gadzzicki; No. 3,298,052, granted Jan. 17, 1967 to Max G. Wolfe; No. 3,497,902, granted Mar. 3, 1970, to John Hartigan; No. 3,604,049, granted Sept. 14, 1971, to Frank W. Hetman; No. 3,775,804, granted Dec. 4, 1973, to Ralph W. Hoener, Jr.; and No. 3,942,213, granted Mar. 9, 1976, to Ralph W. Hoener, Jr. These patents and the prior art that was cited and considered by the Patent Office before granting them and which is listed on the patents should be consulted for the purpose of properly evaluating the subject invention and putting it into proper perspective.